The present disclosure relates to a semiconductor structure and a method of fabricating the same. More specifically, the present disclosure relates to a semiconductor structure including a III-V compound semiconductor material layer that includes a crystalline interlayer as a passivation layer for the III-V compound semiconductor material layer. The present disclosure also provides a method of forming such a semiconductor structure.
Compound semiconductors are semiconductor compounds composed of elements from two or more different groups of the Periodic Table of Elements. For example, III-V (or 13-15) compound semiconductors are composed of elements from Group 13 (B, Al, Ga, In) and from Group 15 (N, P, As, Si, Bi) of the Periodic Table of Elements. The range of possible formulae is quite broad because these elements can form binary alloys (i.e., alloys including two elements, e.g., GaAs), ternary alloys (i.e., alloys containing three elements, e.g., InGaAs) and quaternary alloys (i.e., alloys containing four elements, e.g., AlInGaP).
III-V compound semiconductors, as well as other classes of compound semiconductors, are receiving renewed attention for use as channel materials for advanced ultra large scale integration (ULSI) digital logic applications due to their high electron hole mobility relative to channel materials composed of silicon.
Despite having higher channel mobility than conventional silicon based devices, III-V compound semiconductors when used as the channel region of a metal oxide semiconductor field effect transistor (MOSFET) or other semiconductor devices suffer from a high density of interface states (Dit) which exists between the III-V compound semiconductor material layer and an overlying layer such as, for example, a high k dielectric material layer. A high density of interface states are typically caused when incoming adatoms (such as air, moisture, and/or a high k dielectric material) interact with the III-V compound semiconductor's surface atoms destroying the crystallinity of the III-V surface.
Efforts such as, for example, chemical pre-treatment or an amorphous Si passivation of the III-V compound semiconductor have been tried to reconcile this issue but with only limited successful; the density of interface states is still larger than 1E12/cm2ev.